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GMT Delta Confusion
by Richard L. Shockney June 9, 1999

June 9, 1999

I recently designed a time zone converter and reference site using the excellent database that is maintained at this site. Conversions between time zones appear as expected except when the time zone involves one of the Etc/GMT+ or Etc/GMT- designations. To provide a specific example (and maintain my own sanity) assume the following time zones: GMT, Etc/GMT-5, and US/Central With DST currently in effect, US/Central is 5 hrs behind GMT. Therefore, GMT - US/Central = +5. However, the database indicates that GMT - 'Etc/GMT-5' = -5. Or, stated another way that GMT plus 5 hrs equals Etc/GMT-5 (?) Most people would associate GMT-5 with "the time zone which is 5 hrs behind GMT." However, the database seems to have this defined as "the time zone for which GMT is 5 hrs behind." Can someone confirm that the results I obtained are reproducible? Is there something I do not understand or are the definitions for the Etc/GMT+n and Etc/GMT-n designations reversed in the database? Thanks for your help. Rich Shockney Timezoneconverter.com

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64-bit time_t
by Alan Perry June 8, 1999

June 8, 1999

Not sure if this has been discussed before, has anyone been thinking about the effect of a 64-bit time_t on the zoneinfo file? It seems that just substituting a set of 8-byte values for the transition times could result in really big zoneinfo files, particularly when you consider that there are many more possible transition times. alan perry

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US vs. European Date Notation
by Markus Kuhn June 8, 1999

June 8, 1999

May be someone on this list has some insight about this topic: A journalist of the Wall Street Journal has contacted me as part of his research for a feature article about date notations. He noted that more and more Americans now start to use the European day, month, year notation instead of the traditional month, day, year, and he now realizes that thanks to ISO 8601 all this is moving into the wrong direction anyway. He would be very interested into any pointers of the history of these three date notations, and actually I am quite interested as well. Why do Americans write dates as "December 31, 1999" while Europeans write "31 December 1999", etc.? Why are in East Asia Bigendian dates more common? Markus -- Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK Email: mkuhn at acm.org, WWW: <http://www.cl.cam.ac.uk/~mgk25/>

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DST in the media
by Olson, Arthur David (NCI) May 20, 1999

May 20, 1999

"Good news." "What did they do? Extend Daylight Saving Time year round?" Professional tanner George Hamilton in dialog from a May, 1999 episode of the syndicated television series "Baywatch" --ado

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Time Zones Information
by ZinaFishberg May 19, 1999

May 19, 1999

Dear Sir/Madam: Information systems department of our company (Seabury&Smith) is involved in building a marketing Data Warehouse. We store information on address and phone for all our customers. Part of this information is the Time Zone. We have to be able to uniquely identify the Time Zone based on the area code or address (state, city, or county ). Also, it's important to be able to identify the correct Time Zone for sates and Area Codes that cross Time Zones (for example, North Dakota). Could you, please, provide help to us regarding this matter. Thank you.

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Time Zones Information
by ZinaFishberg May 19, 1999

May 19, 1999

Dear Sir/Madam: Information systems department of our company (Seabury&Smith) is involved in building a marketing Data Warehouse. We store information on address and phone for all our customers. Part of this information is the Time Zone. We have to be able to uniquely identify the Time Zone based on the area code or address (state, city, or county ). Also, it's important to be able to identify the correct Time Zone for sates and Area Codes that cross Time Zones (for example, North Dakota). Could you, please, provide help to us regarding this matter. Thank you.

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FW: Tonga planning DST in year 2000
by Olson, Arthur David (NCI) May 13, 1999

May 13, 1999

Note that Eric Ulevik is not on the time zone mailing list -----Original Message----- From: Eric Ulevik Sent: Monday, May 03, 1999 7:23 AM To: tz(a)elsie.nci.nih.gov Subject: Tonga planning DST in year 2000 Tonga gets serious on millennium bid Monday 3 May, 1999 (1:57pm AEST) Kingdom of Tonga is so determined to be the first country in the world to see 2000 that it might introduce daylight saving this year for the first time ever. Tonga prides itself on being the first country in the world to see the sun each day, although New Zealand catches up with Tonga's time zone each summer. Tonga has great plans to welcome in the year 2000 but its hoped for tourist boom has lost some of its shine because New Zealand is claiming that its Chatham Islands will be the first place in the world to greet the New Year. Tonga's director of tourism, who is also secretary of the National Millenium Committee, has a plan to get Tonga back in front. He has proposed a one-off move to tropical daylight saving for Tonga from October to March, which has won approval in principle from the Tongan Government.

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RE: mktime bug?
by Olson, Arthur David (NCI) May 13, 1999

May 13, 1999

I'm unable to duplicate the problem. --ado Script started on Thu May 13 03:49:04 1999 gertrude$ cat mktimetest.c #include <stdio.h> #include <time.h> #include <errno.h> int main() { struct tm tm; time_t secs; memset(&tm, 0, sizeof tm); tm.tm_year = 99; tm.tm_mon = 4; tm.tm_mday = 13; secs = mktime(&tm); printf("secs: %ld\n", secs); if (secs < 0) printf("strerror(errno): %s\n", strerror(errno)); return 0; } gertrude$ cc mktimetest.c libtz.a -o mktimetest gertrude$ TZ=Europe/Paris ./mktimetest secs: 926550000 gertrude$ TZ=America/New_York ./mktimetest secs: 926571600 gertrude$ TZ=CET-1CEST-2 ./mktimetest secs: 926550000 gertrude$ exit script done on Thu May 13 03:50:23 1999

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FW: mktime bug?
by Olson, Arthur David (NCI) May 13, 1999

May 13, 1999

Be sure to direct replies to Guido, who's not on the time zone mailing list. --ado -----Original Message----- From: Guido Flohr [SMTP:gufl0000@stud.uni-sb.de] Sent: Wednesday, May 12, 1999 8:43 PM To: tz(a)elsie.nci.nih.gov Subject: mktime bug? Hi, sorry, it's me again. I have problems with this little piece of code: bash$ cat >mktimetest <<EOF #include <stdio.h> #include <time.h> int main () { struct tm tm; time_t secs; memset (&tm, 0, sizeof tm); tm.year = 99; tm.mon = 4; tm.mday = 13; secs = mktime (&tm); printf ("secs: %ld (%s)\n", secs, strerror (errno)); return 0; } EOF # make mktimetest # TZ=CET-1CEST-2 ./mktimetest secs: -1 (OK) On installations where summertime applies during May mktime returns an error here (happens somewhere in the function time2). If I set tm.tm_isdst = -1; before calling mktime() the function returns the correct time. I have fixed that by inserting the line tmp->tm_isdst = -1; in mktime() before time1() gets called but I'm not sure if this is the right place to do that (or if this is correct at all). Can you verify that behavior or have I messed up my sources? If it is a bug, how should it be fixed? Thanks Guido -- http://stud.uni-sb.de/~gufl0000 mailto:gufl0000@stud.uni-sb.de

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FW: POSIX-TZ without rules
by Olson, Arthur David (NCI) May 13, 1999

May 13, 1999

Be sure to direct replies to Guido, who's not on the time zone mailing list. --ado -----Original Message----- From: Guido Flohr [SMTP:gufl0000@stud.uni-sb.de] Sent: Monday, April 26, 1999 9:46 PM To: arthur_david_olson(a)nih.gov Subject: POSIX-TZ without rules Hello! I'm the current maintainer of the MiNTLib. The MiNTLib is the standard libc for MiNT and MiNT is a free Unix-clone for Atari computers. I've implemented parts of the tzcode and tzdata packages (version 1998c) in the MiNTLib. This went mostly without problems. Two problems arised: First, for testing purposes I set the envariable TZ to "CET-1CEST-2", i. e. a valid POSIX-style string but without explicit rules. I also uninstalled the database for that test. Under these circumstances tzparse() in localtime.c will return an error because it fails to open a default rules file. From what I remember I would say that POSIX demands that the US rules should be applied instead. Anyway, "CET-1CEST-2" is perfectly POSIX-compliant and the library should not return an error then. The GNU libc handles this case by assuming an implicit rule of "M4.1.0,M10.5.0" (commented as "US Federal Law"). My solution is somewhat different: I generated a header "new_york.h" with the disassembled contents of /usr/share/zoneinfo/posix/America/New_York. Now, not giving rules with no time zone database installed has the same effect as linking posixrules to America/New_York (as recommended in the Makefile of tzcode). The second problem: In zic.c, the analysis of the return value of system("yearistype ...") assumes a certain structure of that return value. I think it would be more portable to use the macros from sys/wait.h instead (although this would probably require an additional -D option to cc that determines whether to use POSIX- or BSD-style macros). May sound pedantic, but here's the story: I have happened to introduce a bug in the waitpid() function of the MiNTLib; the upper two bytes of the status pointer weren't zeroed out but contained some garbage. This affected system() because it calls waitpid. The error message from zic was: wild result 27525120 ... australasia line 75, command was "./yearistype 1990 even" Well, I could figure out what happened, but an average user would have had problems, because typing the command literally into the shell simply returned 0. If I understand the sources correctly, the more common error that the yearistype command is not found (e. g. running "zic -y yearistype ..." without "." in $PATH) would also produce quite confusing error messages (but at least the shell would also complain because you don't redirect stderr to /dev/null). Another argument: The specification for system() explicitely demands to use the wait macros to analyse the return value. These macros would have worked in the above described case. From this point of view the garbage in the upper 2 bytes is not even a bug. Apart from that: Thanks for all the work you must have invested into the time zone database! Everything works perfectly fine here. Ciao Guido -- http://stud.uni-sb.de/~gufl0000 mailto:gufl0000@stud.uni-sb.de

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